Gas pressure operated electric switching device



Nov. 10, 1970 sc o ETAL 3,539,745

GAS PRESSURE OPERATED ELECTRIC SWITCHING DEVICE Filed Nov. 14, 1967 3 Sheets-Sheet 1 INVENTORS. AL 4 E/V &. SCf/OEA/E/ij BY 4 1. A50 4. flAV/SO ATTORNEYS.

Nov. 10, 1970 A. s. SCHOENER ETAL 3,539,745

GAS PRESSURE OPERATED ELECTRIC SWITCHING DEVICE 3 Sheets-Sheet 2 Filed Ndv. 14, 1967 INVENTORS. SCHOE/VE ALLEN 6. ,q BY ELL/SON L. DAV/SON Nov. 10, 1970 A. G; SCHOENER ETAL 3,539,745

GAS PRESSURE OPERATED ELECTRIC SWITCHING DEVICE Filed Nov. 14, 1967 5 Sheets-Sheet 5 \I INVENTORS.

ALLEN G. SCI/OEA/fl? BYELL/SO/V L. DAV/SON United States Patent 3,539,745 GAS PRESSURE OPERATED ELECTRIC SWITCHING DEVICE Allen G. Schoener, Verona, and Ellison L. Davison, Glenshaw, Pa., assignors to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 14, 1967, Ser. No. 682,896 Int. Cl. H01h 35/40 U.S. Cl. 200-83 6 Claims ABSTRACT OF THE DISCLOSURE It is among the objects of this invention to provide an electric switching device, in which a switch is actuated in response to movements of a diaphragm, and in which adjustments can be made to require a greater or lesser pressure against the diaphragm in order to actuate the switch.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a plan view of the switching device with parts broken away in section;

FIG. 2 is an end view taken from the right-hand end of FIG. 1; and

FIG. 3 is a combined vertical section and elevation taken on the line III-III of FIG. 1.

Referring to the drawings a housing has a rigid cylindrical side wall 1 and end walls formed from flexible diaphragms 2 and 3. Diaphragm 2 is held against one end of the side wall by a clamping ring 4 and a collar 5 screwed onto the side wall. Clamped between the collar and ring are the outer edges of the bases of a pair of angle brackets 6 that have flat parallel outwardly extending portions spaced from opposite sides of the axis of the housing. The base of each bracket is cut out to provide an opening 7 (FIG. 2) and the inner end of each outwardly extending portion is recessed at 8 (FIG. 3) so that the bracket will not interfere with outward flexing of the adjacent diaphragm.

Supported between the two brackets, as shown in FIG. 3, is a normally open switch 10. Preferably, the switch is the type that can be closed when a magnet is moved close to it. The leads 11 from the switch are rigidly supported by the inner ends of a pair of vertical metal strips 12 fastened to the opposite ends of an insulating block 13 by screws 14. The block is fastened to the two brackets by bolts 15. The outer ends of strips 12 are connected by wires 16 into an electrical circuit that is closed by closing the switch. The switch preferably is on the axis of the housing, but it is spaced from diaphragm 2 a considerable distance.

In order to close the switch, an actuating member is disposed between it and the adjacent diaphragm for move ment by the latter toward the switch. In the case of a magnetic switch, the actuating member is a magnet 18 supported in an insulating block 19 mounted in an opening of an arm 20 formed from a substantially rigid metal strip. One end of the strip is secured by screws 21 to a shaft 22 that is rotatably mounted in the two brackets, parallel to the diaphragm. The magnet is centered relative to the axis of the housing, so the shaft is located at 'ice one side of that axis. The inner end portion of the strip that forms arm 20 may be bent to form a loop 23 extending considerably closer to the center of the diaphragm.

It will be seen that if gas under sufficient pressure, such as air or oxygen from an intermittent positive pres sure breathing apparatus, is delivered to the inside of the housing through a combined inlet and outlet 25 in the side wall of the housing, as shown in FIGS. 1 and 2, diaphragm 2 will be moved outwardly by the pressure into engagement with the arm 20 and will swing it outwardly far enough for the magnet to act on the switch to close it.

It is another feature of this invention that the resistance of arm 20 to rotation can be increased so that a greater gas pressure in the housing will be required before the switch will close. For this purpose, as shown in FIGS. 1 and 2, the shaft is extended outwardly from one of the brackets 6 and rigidly supports a resilient member, such as a leaf spring 27, that extends laterally away from the shaft toward the opposite side of the housing. This spring can be preloaded to any desired extent in order to cause it to resist movement of the magnet toward the switch. The adjustable preloading can be effected by means engageable with the outer side of the free end portion of the spring. This means most suitably is a cam 28 rigidly mounted on a shaft 29 rotatably supported by the brackets and extending away from the opposite side of the housing. The outer end of the shaft is designed to receive a knob (not shown), by which it can be turned. The position of the cam relative to the spring determines how much resistance the spring will offer to rotation of the shaft 22 that supports the magnet. In order to return the magnet to its initial inoperative position every time the pressure in the housing is reduced and the diaphragm withdrawn, a weak torsion wire spring 30 is coiled around shaft 22, with one end anchored in the adjoining bracket and the other end overlying the central portion of the spring as shown in FIG. 2.

If only one switch is to be operated, diaphragm 3 is not necessary and could be replaced by a rigid end wall, but when a second switch 32 is used, this diaphragm is required. It is clamped in place by a ring 33 and a collar 34. The collar also clamps a pair of spaced parallel angle brackets 35 to the housing and these brackets support an insulating block 36 between them. The block supports switch 32, which preferably is a normally open magnetic switch. Between the switch and the diaphragm there is a magnet 37 that is carried by an insulating block 38 mounted in an arm 39 (FIG. 1) projecting from a shaft 40 rotatably mounted in the two brackets. The shaft extends away from one of the brackets and supports one end of a leaf spring 41. A spring normally is held substantially parallel to the housing by a light torsion spring 42. Resistance to movement of the magnet toward the switch is controlled by a cam 43 mounted on one end of a shaft 44 journaled in the two brackets. When the shaft is turned to move the cam into engagement with the spring, any desired amount of preloading can be exerted on the spring.

When this switching device is used in monitoring intermittent positive pressure breathing apparatus, switch 32 may be connected into an electric circuit that monitors the breathing rate and the minimum pressure, while the other switch 10 is connected into a circuit that monitors the maximum pressure in the system. To prevent a sudden but transitory increase in pressure from actuating switch 10, a vertical partition 47 is mounted inside the housing between the inlet 25 and diaphragm 2. This partition divides the inside of the housing into two chambers which are connected by an aperture 48 in the partition. If the patient should cough and thereby suddenly increase the pressure in the larger chamber, this pressure will be prevented by the partition from reaching the other chamber and closing switch 10. That is, before the momentary increased pressure in the large chamber can be transmitted through the small hole in the partition to the other chamber, the breathing apparatus will have switched to the exhalation cycle and the pressure in the housing will be reduced.

According to the provisions of the patent statutes, we

V have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the ap pended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

.1. A gas pressure operated electric switching device comprising a housing provided with an inlet and outlet for a gas, a flexible diaphragm forming a wall of the housing and responsive to gas pressure therein, a switch spaced from the diaphragm, switch-actuating means disposed between the diaphragm and switch, movable means supporting said actuating means for movement by the diaphragm toward the switch far enough to actuate the switch, resilient means, means rigidly connecting the resilient means to said movable means for movement of the resilient means by said movable means, and means independent of said connecting means for varying the resistance of said resilient means to movement by said movable means.

2. A device as recited in claim 1, in which said independent means is a cam.

3. A gas pressure operated electric switching device comprising a housing provided with an inlet and outlet for a gas, a flexible diaphragm forming a wall of the housing and responsive to gas pressure therein, a switch spaced from the diaphragm, a switch actuating member disposed between the diaphragm and switch, a rotatable shaft parallel to the diaphragm, an arm projecting laterally from said shaft and carrying said actuating member, the arm being movable by the diaphragm to turn the 40 shaft and swing the actuating member far enough to actuate the switch, and means operatively connected to said shaft for varying its resistance to turning.

4. A device as recited in claim 3, in which said resistance-varying means include a leaf spring rigidly connected at one end to said shaft, and an adjustable cam for preloading the spring.

5. A device as recited in claim 4, including bracket means secured to the housing and overlying said diaphragm in spaced relation thereto, and means fastening said switch to said bracket means, said shaft being journaled in said bracket means with said actuating member disposed substantially in axial alignment with the diaphragm and normally spaced from the switch.

6. A gas pressure operated electric switching device comprising a housing provided with an inlet and outlet for a gas, a flexible diaphragm forming a wall of the housing and responsive to gas pressure therein, a switch spaced from the diaphragm, switch actuating means disposed between the diaphragm and switch, movable means supporting said actuating means for movement by the diaphragm toward the switch far enough to actuate the switch, means for varying the resistance of said movable means to movement by the diaphragm, a second flexible diaphragm forming the wall of said housing opposite said first-mentioned diaphragm, a switch spaced from the second diaphragm, switch-actuating means disposed between the second diaphragm and switch, movable means supporting the second actuating means for movement by the second diaphragm toward the second switch far enough to actuate that switch, and a partition in said housing at one side of said inlet and outlet, the partition dividing the inside of the housing into two chambers and being provided with an aperture connecting them.

References Cited UNITED STATES PATENTS 6/ 1948 1/ 1959 1/ 1965 Dietz.

2/ 1968 Wolford.

Kocmich. Bobo. 

